This invention relates to a cylinder head for an outboard motor and more particularly to an improved cylinder head and induction system for a four-cycle internal combustion engine as employed in an outboard motor.
As is well known, the powering internal combustion engine of an outboard motor is normally mounted in the power head so that the output or crankshaft rotates about a vertically extending axis for ease of coupling to the drive shaft. With such an arrangement, the cylinders are horizontally disposed and this normally means that the induction passages that supply the combustible mixture to the cylinders also extend generally horizontally. Horizontal disposition of the induction system has certain disadvantages, particularly when employed with outboard motors.
Outboard motors frequently run at speeds lower than idle speed, for example when trolling. Under this condition, the rate of airflow through the induction passage is quite slow and any fuel in the induction system may tend to condense and form as puddles in the intake manifold. When this occurs, the collected fuel can be delivered intermittently to the combustion chambers and cause uneven running.
Therefore, it is normally the practice with an outboard motor to dispose the induction system so that it is inclined slightly downwardly from its inlet into its discharge end.
With four-cycle practice in outboard motors, the induction system normally extends along a side of the engine and the inlet device is disposed adjacent or even beyond the crankcase relative to the cylinder block. However, with the use of downward inclination to the induction system, then the portion of the engine becomes quite high. This has a number of disadvantages. Also, since the inlet to the induction system is normally disposed to the front of the outboard motor, the necessary high front of the protective cowling dictated by the configuration of the induction system is even more objectionable.
If, however, the downward inclination is not employed, then the problems with fuel collection and irregular running will result.
It is, therefore, a principal object of this invention to provide an improved induction system for an outboard motor.
It is a further object of this invention to provide an improved induction system for a four-cycle engine as employed in an outboard motor wherein the induction system can have a downward inclination to avoid fuel collection without raising the overall height of the engine.